The field of this invention is sprayable cookware lubricant compositions which are applied to the inside of pans used for baking bread, cakes, etc. to promote the release of the baked product from the pans. One standard practice which has been used many years by cooks is to apply a coating of a solid or liquid fat or oil to the inside of the pan, and then to dust the coating with flour. Formulas and products have also been developed for applying pre-mixed compositions by aerosol or pump-type sprays. In particular, lecithin has been proposed for use in such compositions as a pan release agent. See U.S. Pat. Nos. 3,038,816, 3,661,605, 3,896,975, and 4,073,411.
U.S. Pat. No. 3,038,816 described an aerosol preparation for use as a cookware lubricant which is composed primarily of lecithin dissolved in a fluorocarbon propellant. This system depends on the solubility of the lecithin in the propellant, and is not adapted to the use of hydrocarbon propellants as now preferred for reasons of environmental protection. Water dispersible forms of lecithin, such as hydroxylated lecithin, can be dispersed in water, which is then emulsified with a vegetable oil, and the emulsion pressurized with a hydrocarbon propellant, as described in U.S. Pat. No. 3,661,605. U.S. Pat. No. 3,896,975 discloses a non-foaming water-in-oil emulsion using lecithin selected for its low HLB number. U.S. Pat. No. 4,073,411 also discloses a water-in-oil lecithin emulsion which is claimed to provide improved freeze-thaw stability.
Proposals have also been made for cookware lubricant compositions containing fats or oils together with flour or starch. See U.S. Pat. Nos. 2,210,043 and 3,821,007. One problem with such compositions is the tendency of the starch or flour particles to separate on standing. According to U.S. Pat. No. 3,821,007 a normally solid vegetable fat can be used in combination with a liquid fat to assist in maintaining the suspension of the flour. The formula disclosed therein contains about 25% by weight of flour (wheat and soybean). This preparation would be very difficult to dispense from an aerosol container because of its content of solid fat and the high proportion of particulate solids. Where this composition is formulated with a hydrocarbon propellant to avoid use of a freon-type propellant, it has been found that severe packing, clogging, and billowing problems are encountered.
The present invention utilizes a vegetable oil solution of lecithin, or other emulsifier in admixture with a hydrocarbon propellant, such as isobutane, as a sprayable cookware lubricant. This mixture provides a single liquid phase which foams on application. Because of the translucency of the single liquid phase, it is difficult to visually determine that a thin, uniform coating of the lubricant composition is being applied to the inside of the baking container. Over-application of the lubricant in some areas results with consequent run-down of the liquid, and under-application in other areas results in an insufficient release action. However, it has been found that the ease with which a uniform application can be visually-directed is greatly improved by incorporating a limited but significant amount of particles of white flour or white starch in the composition. These solid phase particles reflect the light, permitting the coating distribution and thickness to be much more readily observed by the person applying the aerosol composition.
There is a further related problem. The particles of flour or starch tend to settle rapidly out of the single liquid phase requiring repeated shaking of the aerosol container to assure that there will be a relatively uniform distribution of the white particles in the spray being applied. Further, when the concentration of flour, or a mixture of flour and starch, is increased to as much as 25 to 30% by weight of the total composition, the settled particles tend to pack into the form of a cake, which is difficult to redisperse by shaking the container. Further, when only partial redistribution is obtained, the aggregates of particles can result in clogging of the valve of the aerosol dispenser.
It has been found that the advantage of having the particles of flour or starch present as a visual indicator can be obtained without the disadvantages just referred to providing the concentration of the flour and starch is limited to no more than 15% by weight of the total composition. The most desirable concentration for the purpose of this invention is found to be in the range from 2 to 10%. Moreover, the ease with which the white particles of flour or starch can be resuspended and maintained as a relatively uniform distribution during spraying is promoted by the incorporation of a small amount of fumed silica. Thus the problems of container packing and valve clogging are avoided. Also, the presence of the fumed silica increases the viscosity of the composition without interfering with its sprayability, thereby effectively controlling spray billowing on application.